Avoid soil compaction when grazing cover crops. | Latest news on corn, soybeans, wheat and more
Cover crops are considered to be one of the most effective and economical ways to improve soil health. Grazing them can be a way to turn them into profit for your operation. It is important, however, to avoid causing excessive compaction which could adversely affect the yield of subsequent crops and increase runoff and erosion.
Sjoerd Duiker, Soil Management Specialist at Penn State Extension, offers some tips for avoiding excessive compaction when grazing cover crops:
Use continuous seeding first. No-till soil is more resistant to compaction than tilled soil. Even two or three years after tillage, the soil will still be softer, resulting in greater pugging by grazing animals. The high organic matter content near the continuous no-till surface does not compact easily. Make sure the cover culture medium is dense. A dense cover crop has a robust root system that will help resist compaction.
And rotation with perennials is important. Perennial crops such as orchard grass, fescue, brome, alfalfa, or red clover improve the soil beyond what is possible with an annual. The effect of the perennial lasts for many years. Rotating with taproot crops like alfalfa, red clover, sweet clover or chicory helps improve subsoil porosity.
It is important to feed the “underground herd”. This means stimulating fungal and bacterial activity and promoting soil animals like earthworms which create macropores in the soil.
Leave enough crop residue after grazing to nourish the soil. Healthy soil with high biological activity will rebound faster after any compaction caused.
Have a mobile water source. Most compaction is usually caused near the water source. By moving it regularly, you limit the potential for soil compaction.
Monitor soil moisture conditions and do not graze in excessively wet areas. You can use a ball test to determine if the soil is suitable for accommodating animals by grabbing a handful of top soil and kneading it in your hand. If it forms a ball, the soil is too wet. If the soil conditions are marginal, you need to ask yourself if there are any fields on your farm that drain faster than others. You might have sandy or shale soil, which drains faster, which might be ready sooner than limestone soil or soil with a high seasonal water table.
Steep sloping soils can also be a problem during wet times of the year. When the hooves start to skid down the slope or create ridges, it is time to move the animals to flatter fields.
Move animals more frequently when the soil is wet to reduce exposure time. This means that you pack the herd into a smaller area, but stay there for a shorter period. Rear fencing is a good idea no matter what, so animals don’t come back to an area that has already been grazed.
Move animals to perennial pastures with difficult root systems if conditions are wet. You will quickly notice the difference between hard rooted species like tall, chewy or red fescue pastures and annual cover crops that have a smaller root system. Perennial grass is much more resistant to compaction. Remove animals if you expect them to cause severe compaction. This is a last resort, but it is best to put some mud in your field.
Now is the time to check for damage to your emerged soybeans.
Some growers notice damage to their newly emerged soybeans.
Kiersten Wise of Purdue University says the fungicide fluopyram (ILeVO) is currently marketed as a seed treatment to manage sudden death syndrome. Treatment may result in soybean cotyledon discoloration which may resemble disease or other abiotic stress such as herbicide damage. The discoloration occurs because the fungicide is moderately systemic in the soybean plant, so it will naturally travel to the plant’s wells, roots, and cotyledons.
This build-up can lead to phytotoxicity, causing a yellow-brown staining of the ends of the cotyledons. This necrosis is generally uniform and present on every plant grown from a seed treated with ILeVO. However, environmental conditions can impact the frequency, consistency and severity of the phytotoxicity observed.
Phytotoxicity is generally not found on unifoliate or trifoliate leaves. Research by several granting universities and the Ontario Ministry of Agriculture, Food and Rural Affairs has shown that this phytotoxicity, also known as the halo effect, does not cause growth retardation at long-term soybean or loss of yield.
Preemergence herbicides can also cause damage to soybean seedlings, especially when cool temperatures coincide with rain soon after seedlings begin to emerge from the soil. Pre-emergent herbicides, usually PPO inhibitors (flumioxazin, sulfentrazone, saflufenacil; group 14) or photosynthesis inhibitors (metribuzin; group 5), can sometimes harm plants growing in cold, wet soils. Soybeans are generally able to metabolize these herbicides, but when the metabolism slows down due to stress, such as cold temperatures, herbicide damage can occur.
Pre-emergence herbicide damage also occurs when heavy rains splash concentrated droplets of residual soil herbicide onto emerged seedlings. Spotted necrosis can occur on any exposed part of the plant where the splash event occurred, and metribuzin can cause symptoms similar to the phytotoxicity caused by ILeVO.
Seedling blight damage like pythium root rot, pre-emergence herbicides, and ILeVO can look very similar. ILeVO damage is usually only found on the surface of the cotyledons, so break a few cotyledons and look for green inside to distinguish them from other injuries or diseases.
If you are still unsure of the cause of the damage found, send a sample to a local diagnostic lab. Obtaining an accurate diagnosis will allow you to determine the best management strategies for your soybean field.